Israel launched an attack on Iran, American media reported, citing US government officials, while Iranian state media reported that explosions were heard early Friday near the central city of Isfahan, Radio Free Europe reported in English.
Israeli officials announced that they would retaliate against Iran's attack, which launched more than 14 drones and missiles at Israel on April 300, almost all of which were shot down.
Video posted on CNN television and social media shows several large explosions said to be near Isfahan.
Iran's state news agency IRNA said the air defense systems fired from a major airbase in Isfahan that houses Iran's aging fleet of US-made F-14 Tomcats, bought before the 1979 Islamic Revolution.
Isfahan also has facilities that are part of Iran's nuclear program, including the Natanz underground uranium enrichment facility.
IRNA did not provide other details and it could not be independently confirmed that Israel launched the attack.
Iranian state television reported that air defense systems fired in several provinces with reports of drone flights.
No official in Tehran has directly acknowledged that Iran was attacked, while the Israeli military has not made any announcements.
Almost all drones and missiles launched by Iran at Israel on April 14 were shot down by Iranian forces with the help of US, French, British and Jordanian forces.
Tehran's attack was expected in Israel after an airstrike on the Iranian embassy compound in Damascus, Syria, on April 1 killed seven members of the Revolutionary Guard, including two generals.
Since then, diplomats and politicians around the world, fearing another escalation of fighting in the Middle East, have called for restraint while awaiting Israel's response.
Prime Minister Benjamin Netanyahu said this week that Israel will decide how and whether to respond to Iran's attack.
Attacks on military positions in the south of Syria
Israeli forces targeted the position of the Syrian army in the south of Syria early this morning, the Observatory for Human Rights (OSDH) announced.
"The Israeli strikes targeted a Syrian army radar position between Sueida and Deraa provinces," OSDH director Rami Abdel Rahmane said.
He added that the attacks were "at a time when Israeli planes were intensively flying over the Deraa region", and that the Syrian air defenses were not activated.
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